research communications
Synthesis, E)-3-hydroxy-2-methyl-6-(quinolin-8-yldiazenyl)phenolato]copper(II) monohydrate
and photophysical properties of chlorido[(aDepartment of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
*Correspondence e-mail: chihiro.kachi@chem.sci.toho-u.ac.jp
The reaction between copper(II) chloride dihydrate and the (E)-2-methyl-4-(quinolin-8-yldiazenyl)benzene-1,3-diol ligand in acetonitrile leads to the formation of the title compound, [Cu(C16H12N3O2)Cl]·H2O. The ligand is deprotonated and coordinates with three donor atoms (tridentate) to the CuII ion. Individual molecules of the CuII complex are connected by chloride bridges, forming a one-dimensional coordination polymer. No to the cis isomer of the azo ligand was observed upon irradiation with UV light.
Keywords: crystal structure; copper(II) complex; quinoline-based azo ligand; electronic absorption spectra.
CCDC reference: 2162331
1. Chemical context
Azobenzene derivatives are well-known dyes with fascinating characteristics such as cis–trans and azo–hydrazone The combination of with metal ions to form complexes is a promising approach for controlling their photophysical properties. In metal complexes with azo ligands, the metal centers and azo ligands can affect each other's properties. For example, cis–trans by irradiation with a single frequency of light has been achieved in azo-conjugated metal complexes by a combination of the photophysical and the redox properties of ligand and metal center (Nishihara, 2005). Azobenzene derivatives with hydroxy groups in the ortho or para position tend to form hydrazone tautomers (Jacques et al., 1979; Ball & Nicholls, 1982; Rauf et al., 2015). A hydrazone tautomer can be converted to an azo tautomer by complexation to the metal ion (Chen et al., 2012; Cai et al., 2016). In this study, we used the ortho and para isomer of the hydroxy-substituted azobenzene derivative, (E)-2-methyl-4-(quinolin-8-yldiazenyl)benzene-1,3-diol, to investigate azo–hydrazone in its CuII complex. The photophysical properties of the ligand and the CuII complex were studied by UV–Vis spectroscopy to address the potential photoisomerization.
2. Structural commentary
The II complex is shown in Fig. 1. The contains one CuII complex and one solvent water molecule. The hydroxy group in the ortho-position of the azo ligand is deprotonated and is coordinated the CuII center. In the the CuII ion is 4-coordinated in a distorted square-planar geometry. The donor atoms comprise one nitrogen atom of the quinoline moiety, one nitrogen atom of the azo group, one deprotonated alcohol oxygen atom, and a chloride ion. The other hydroxy group of the azo ligand, in the para-position, remains protonated. The chlorido ligand is also weakly coordinated by an adjacent CuII center occupying its apical position, resulting in an elongated square-pyramidal around the copper(II) ions. The Cu1—Cl1i distance in the apical position is 2.7395 (10) Å, which is notably longer than the distances in the equatorial positions, Cu1—Cl1 = 2.2803 (8) Å, Cu1—O1 = 1.917 (2) Å, Cu1—N1 = 2.008 (3) Å, and Cu1—N2 = 1.945 (3) Å [symmetry code: (i) x + 1, y, z]. The N2—N3 bond distance of 1.293 (4) Å is typical for the N=N double bond of an azo group. The structural features of the aromatic rings and the C11—O1 single-bond length of 1.300 (4) Å also indicate that the ligand adopts the azo structure, rather than the hydrazone structure, which is similar to the structures observed in analogous azo-metal complexes with other metals, including Ni, Cu, and Zn (Cai et al., 2016; Kochem et al., 2011, 2014).
of the Cu3. Supramolecular features
The coordinated chloride ion bridges adjacent CuII complexes to form a one-dimensional coordination polymer resulting in columns along the crystallographic a-axis direction (Fig. 2). This is supported by π–π stacking between the co-planar quinoline rings with a centroid–centroid distance of 3.7711 (4) Å, an inter-plane distance of 3.3494 (12) Å, and a slippage of 1.733 (2) Å. The 1D columns are linked through hydrogen bonds facilitated by the solvent water molecules, C14—H14⋯O3, O2—H2A⋯O3, O3—H3W⋯Cl1i, and O3—H4W⋯O1ii, [symmetry codes: (i) x + , −y + , z − ; (ii) x − , −y + , z − ] (Table 1, Fig. 3).
4. Database survey
A search of the Cambridge Structural Database (CSD Version 5.42, update of November 2020; Groom et al., 2016) with ConQuest (Version 2020.3.0; Bruno et al., 2002) for phenyl- and quinolinyl-bearing azo ligands with an ortho-hydroxy substituent and their complexes resulted in only seven hits. These structures include one ligand derivative and six transition-metal complexes (an azobenzene derivative and its Zn complex, refcodes ONOKUY and ONOLAF; Kochem et al., 2011; Cu complexes, refcodes MOGLAX and MOGLEB; Kochem et al., 2014; an Re complex, refcode TOZTUZ; Sarkar et al., 2015; a Co complex, refcode VARQUD; Taylor et al., 2017; an Ho complex, refcode NAMJIY; Taylor et al., 2018). While co-planarity of the aromatic moieties was observed in some of these structures, the formation of the column-type coordination polymeric structure of the title compound has no precedence in this group.
5. UV–Vis spectra for the azo ligand and CuII complex
The UV–Vis spectra of the azo ligand and the CuII complex in CH3CN are shown in Fig. 4. The maximum of the extinction (ɛmax) was observed at 406 nm for the ligand, while the CuII complex showed decreased absorption and red-shifted maxima at 420 and 489 nm. To investigate the of the ligand and the CuII complex, the samples were irradiated at maximum wavelength, but no to the cis isomer was observed for either compound.
6. Synthesis and crystallization
To synthesize the title ligand, an aqueous solution of 1.2 M NaNO2 (3 mL) was slowly added to a cold solution of 8-aminoquinoline (0.432 g, 3.00 mmol) in 0.5 M HCl(aq) (20 mL). The resulting solution was stirred at 277 K for 15 min, and an aqueous solution of (NH2)2CO (0.180 g, 3.00 mmol) in 3 mL of water was then added to give a diazonium chloride solution. This solution was added to an aqueous 0.25 M NaOH solution of 2,6-dihydroxytoluene (0.372 g, 3.00 mmol) and stirred at 277 K for 30 min and then stirred at room temperature for 15 h. The reaction mixture was acidified with 1 M HCl(aq) (10 mL) and a red precipitate was formed. The precipitate was filtered off and washed with water and then with cold tetrahydrofuran. Yield, 86% (0.787 g, 2.58 mmol). IR: νmax (KBr): 3400, 3068, 1633, 1536, 1503, 1488, 1447, 1364, 1299, 1212, 787 cm−1. 1H NMR (400 MHz, CD3CN): δH 9.06 (d, 1H), 8.41 (d, 1H), 8.20 (d, 1H), 7.97 (d, 1H), 7.74 (t, 1H), 7.62 (dd, 1H), 7.49 (d, 1H), 6.63 (d, 1H), 2.12 (s, 3H). Analysis calculated for C16H13N3O2·0.72HCl: C, 62.90; H, 4.53; N, 13.75. Found: C, 62.49; H, 4.31; N, 14.17. The CuII complex was obtained as a brown solid by the reaction of the azo ligand synthesized as described above (0.099 g, 0.324 mmol) in 4 mL of ethanol with CuCl2·2H2O (0.061 g, 0.358 mmol) in 2 mL of H2O. Yield, 54% (0.073 g, 0.193 mmol). Crystals of the CuII complex suitable for the X-ray crystallography study were obtained by the slow diffusion of a CH3CN solution of the ligand into an aqueous solution of CuCl2·2H2O. IR: νmax (KBr): 3418, 2924, 2854, 1633, 1557, 1508, 1436, 1283, 1258, 1048 cm−1. Analysis calculated for C16H12ClCuN3O2: C, 50.94; H, 3.21; N, 11.14. Found: C, 50.82; H, 3.63; N, 11.49.
7. Refinement
Crystal data, data collection and structure . All non-hydrogen atoms were refined anisotropically. The O—H hydrogen atoms of the solvent water molecules and the hydroxy group in the para-position were found in the difference-Fourier map and were refined isotropically without restraints or constraints. Other hydrogen atoms were generated geometrically, and refined with a riding model with C—H = 0.98 Å, Uiso(H) = 1.5 Ueq(C) for methyl, and C—H = 0.95 Å, Uiso(H) = 1.2 Ueq(C) for aromatic hydrogen atoms. Two reflections were omitted as clear outliers.
details are summarized in Table 2Supporting information
CCDC reference: 2162331
https://doi.org/10.1107/S2056989022003437/yz2018sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022003437/yz2018Isup2.hkl
Data collection: APEX2 (Bruker, 2014); cell
SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2017/1 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).[Cu(C16H12N3O2)Cl]·H2O | F(000) = 804 |
Mr = 395.29 | Dx = 1.758 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 3.7711 (4) Å | Cell parameters from 1510 reflections |
b = 26.451 (3) Å | θ = 2.7–24.3° |
c = 15.0864 (15) Å | µ = 1.66 mm−1 |
β = 97.100 (2)° | T = 100 K |
V = 1493.3 (3) Å3 | Plate, brown |
Z = 4 | 0.44 × 0.09 × 0.02 mm |
Bruker APEXII CCD diffractometer | 2132 reflections with I > 2σ(I) |
φ and ω scans | Rint = 0.049 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | θmax = 25.4°, θmin = 2.1° |
Tmin = 0.629, Tmax = 0.745 | h = −4→4 |
8133 measured reflections | k = −21→31 |
2746 independent reflections | l = −17→18 |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.036 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.081 | w = 1/[σ2(Fo2) + (0.0286P)2 + 0.6665P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max = 0.001 |
2746 reflections | Δρmax = 0.42 e Å−3 |
230 parameters | Δρmin = −0.41 e Å−3 |
0 restraints |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.9143 (9) | 1.03984 (12) | 0.8827 (2) | 0.0157 (7) | |
H1 | 0.822246 | 1.026099 | 0.933371 | 0.019* | |
C2 | 0.9909 (9) | 1.09143 (12) | 0.8821 (2) | 0.0162 (7) | |
H2 | 0.951775 | 1.111932 | 0.931701 | 0.019* | |
C3 | 1.1222 (9) | 1.11240 (12) | 0.8101 (2) | 0.0176 (8) | |
H3 | 1.174056 | 1.147528 | 0.809169 | 0.021* | |
C4 | 1.1803 (9) | 1.08129 (12) | 0.7369 (2) | 0.0146 (7) | |
C5 | 1.3129 (9) | 1.09847 (12) | 0.6585 (2) | 0.0156 (8) | |
H5 | 1.371662 | 1.133133 | 0.652668 | 0.019* | |
C6 | 1.3564 (8) | 1.06562 (12) | 0.5914 (2) | 0.0154 (7) | |
H6 | 1.440700 | 1.077948 | 0.538699 | 0.018* | |
C7 | 1.2798 (8) | 1.01391 (12) | 0.5981 (2) | 0.0140 (7) | |
H7 | 1.314425 | 0.991581 | 0.550631 | 0.017* | |
C8 | 1.1548 (8) | 0.99580 (12) | 0.6736 (2) | 0.0124 (7) | |
C9 | 1.0988 (8) | 1.02935 (12) | 0.7434 (2) | 0.0127 (7) | |
C10 | 1.0113 (9) | 0.86492 (12) | 0.6316 (2) | 0.0140 (7) | |
C11 | 0.8938 (8) | 0.83965 (12) | 0.7082 (2) | 0.0132 (7) | |
C12 | 0.8113 (9) | 0.78725 (12) | 0.7008 (2) | 0.0151 (7) | |
C13 | 0.8379 (9) | 0.76272 (12) | 0.6209 (2) | 0.0164 (8) | |
C14 | 0.9591 (9) | 0.78717 (13) | 0.5468 (2) | 0.0184 (8) | |
H14 | 0.979522 | 0.768954 | 0.493360 | 0.022* | |
C15 | 1.0453 (9) | 0.83666 (12) | 0.5529 (2) | 0.0160 (7) | |
H15 | 1.130421 | 0.852982 | 0.503555 | 0.019* | |
C16 | 0.6924 (9) | 0.75947 (12) | 0.7792 (2) | 0.0180 (8) | |
H16A | 0.534473 | 0.731513 | 0.757445 | 0.027* | |
H16B | 0.563395 | 0.782752 | 0.814287 | 0.027* | |
H16C | 0.901857 | 0.746056 | 0.816731 | 0.027* | |
Cl1 | 0.5361 (2) | 0.92919 (3) | 0.91540 (5) | 0.0160 (2) | |
Cu1 | 0.90089 (11) | 0.93390 (2) | 0.80589 (2) | 0.01287 (13) | |
H2A | 0.747 (11) | 0.7051 (16) | 0.563 (3) | 0.045 (14)* | |
H3W | 0.853 (12) | 0.6570 (17) | 0.448 (3) | 0.043 (18)* | |
H4W | 0.533 (15) | 0.674 (2) | 0.412 (4) | 0.09 (2)* | |
N1 | 0.9636 (7) | 1.00915 (10) | 0.81610 (16) | 0.0126 (6) | |
N2 | 1.0654 (7) | 0.94509 (10) | 0.69027 (17) | 0.0141 (6) | |
N3 | 1.0982 (7) | 0.91430 (10) | 0.62523 (17) | 0.0131 (6) | |
O1 | 0.8645 (6) | 0.86267 (8) | 0.78313 (14) | 0.0157 (5) | |
O2 | 0.7473 (7) | 0.71334 (9) | 0.61565 (17) | 0.0225 (6) | |
O3 | 0.7360 (10) | 0.67746 (11) | 0.44880 (19) | 0.0275 (7) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0175 (19) | 0.0184 (18) | 0.0110 (16) | 0.0034 (15) | 0.0011 (14) | 0.0007 (15) |
C2 | 0.0185 (19) | 0.0147 (18) | 0.0144 (17) | 0.0026 (15) | −0.0016 (15) | −0.0033 (15) |
C3 | 0.023 (2) | 0.0077 (17) | 0.0206 (18) | 0.0023 (14) | −0.0033 (15) | −0.0017 (15) |
C4 | 0.0135 (18) | 0.0114 (17) | 0.0180 (17) | 0.0024 (14) | −0.0012 (15) | 0.0000 (14) |
C5 | 0.0162 (19) | 0.0076 (17) | 0.0223 (19) | −0.0023 (14) | −0.0001 (15) | 0.0044 (15) |
C6 | 0.0148 (18) | 0.0175 (18) | 0.0136 (16) | −0.0015 (15) | 0.0006 (14) | 0.0045 (15) |
C7 | 0.0126 (17) | 0.0162 (18) | 0.0136 (16) | 0.0003 (14) | 0.0029 (14) | −0.0019 (15) |
C8 | 0.0114 (17) | 0.0126 (17) | 0.0131 (16) | 0.0020 (14) | 0.0004 (13) | 0.0018 (14) |
C9 | 0.0106 (17) | 0.0144 (18) | 0.0122 (16) | 0.0017 (13) | −0.0027 (14) | −0.0006 (14) |
C10 | 0.0137 (18) | 0.0123 (17) | 0.0160 (17) | 0.0007 (14) | 0.0010 (14) | −0.0014 (14) |
C11 | 0.0107 (17) | 0.0137 (17) | 0.0145 (16) | 0.0017 (14) | −0.0011 (14) | 0.0000 (14) |
C12 | 0.0168 (19) | 0.0120 (17) | 0.0168 (17) | −0.0014 (14) | 0.0029 (14) | −0.0002 (15) |
C13 | 0.020 (2) | 0.0086 (17) | 0.0205 (18) | 0.0002 (14) | 0.0003 (15) | −0.0002 (15) |
C14 | 0.025 (2) | 0.0156 (18) | 0.0142 (17) | 0.0045 (15) | 0.0025 (15) | −0.0033 (15) |
C15 | 0.0218 (19) | 0.0124 (18) | 0.0142 (16) | −0.0021 (15) | 0.0043 (15) | −0.0009 (15) |
C16 | 0.022 (2) | 0.0126 (17) | 0.0196 (18) | −0.0015 (15) | 0.0036 (16) | −0.0004 (15) |
Cl1 | 0.0190 (4) | 0.0161 (4) | 0.0137 (4) | 0.0011 (4) | 0.0049 (3) | 0.0009 (3) |
Cu1 | 0.0193 (2) | 0.0089 (2) | 0.0110 (2) | −0.00015 (17) | 0.00432 (16) | −0.00005 (17) |
N1 | 0.0161 (15) | 0.0102 (14) | 0.0112 (13) | 0.0040 (12) | 0.0011 (12) | −0.0001 (12) |
N2 | 0.0178 (16) | 0.0110 (14) | 0.0141 (14) | −0.0007 (12) | 0.0046 (12) | 0.0001 (12) |
N3 | 0.0165 (16) | 0.0110 (14) | 0.0115 (14) | −0.0005 (12) | 0.0004 (12) | −0.0012 (12) |
O1 | 0.0262 (14) | 0.0087 (11) | 0.0130 (11) | −0.0012 (10) | 0.0051 (10) | −0.0013 (10) |
O2 | 0.0403 (17) | 0.0093 (13) | 0.0195 (14) | −0.0043 (11) | 0.0095 (12) | −0.0056 (11) |
O3 | 0.040 (2) | 0.0172 (15) | 0.0252 (15) | −0.0017 (15) | 0.0047 (15) | −0.0014 (13) |
C1—N1 | 1.323 (4) | C11—O1 | 1.300 (4) |
C1—C2 | 1.395 (5) | C11—C12 | 1.422 (4) |
C1—H1 | 0.9500 | C12—C13 | 1.383 (4) |
C2—C3 | 1.366 (4) | C12—C16 | 1.506 (4) |
C2—H2 | 0.9500 | C13—O2 | 1.350 (4) |
C3—C4 | 1.416 (4) | C13—C14 | 1.417 (4) |
C3—H3 | 0.9500 | C14—C15 | 1.349 (4) |
C4—C9 | 1.414 (4) | C14—H14 | 0.9500 |
C4—C5 | 1.415 (4) | C15—H15 | 0.9500 |
C5—C6 | 1.359 (4) | C16—H16A | 0.9800 |
C5—H5 | 0.9500 | C16—H16B | 0.9800 |
C6—C7 | 1.404 (4) | C16—H16C | 0.9800 |
C6—H6 | 0.9500 | Cl1—Cu1 | 2.2803 (8) |
C7—C8 | 1.372 (4) | Cl1—Cu1i | 2.7395 (10) |
C7—H7 | 0.9500 | Cu1—O1 | 1.917 (2) |
C8—C9 | 1.412 (4) | Cu1—N2 | 1.945 (2) |
C8—N2 | 1.413 (4) | Cu1—N1 | 2.008 (3) |
C9—N1 | 1.374 (4) | N2—N3 | 1.293 (3) |
C10—N3 | 1.353 (4) | O2—H2A | 0.82 (4) |
C10—C15 | 1.423 (4) | O3—H3W | 0.70 (4) |
C10—C11 | 1.451 (4) | O3—H4W | 0.89 (6) |
N1—C1—C2 | 123.2 (3) | O2—C13—C12 | 117.4 (3) |
N1—C1—H1 | 118.4 | O2—C13—C14 | 119.9 (3) |
C2—C1—H1 | 118.4 | C12—C13—C14 | 122.6 (3) |
C3—C2—C1 | 119.9 (3) | C15—C14—C13 | 119.2 (3) |
C3—C2—H2 | 120.1 | C15—C14—H14 | 120.4 |
C1—C2—H2 | 120.1 | C13—C14—H14 | 120.4 |
C2—C3—C4 | 119.4 (3) | C14—C15—C10 | 121.4 (3) |
C2—C3—H3 | 120.3 | C14—C15—H15 | 119.3 |
C4—C3—H3 | 120.3 | C10—C15—H15 | 119.3 |
C9—C4—C5 | 118.2 (3) | C12—C16—H16A | 109.5 |
C9—C4—C3 | 117.0 (3) | C12—C16—H16B | 109.5 |
C5—C4—C3 | 124.8 (3) | H16A—C16—H16B | 109.5 |
C6—C5—C4 | 120.3 (3) | C12—C16—H16C | 109.5 |
C6—C5—H5 | 119.8 | H16A—C16—H16C | 109.5 |
C4—C5—H5 | 119.8 | H16B—C16—H16C | 109.5 |
C5—C6—C7 | 121.6 (3) | Cu1—Cl1—Cu1i | 96.97 (3) |
C5—C6—H6 | 119.2 | O1—Cu1—N2 | 90.72 (10) |
C7—C6—H6 | 119.2 | O1—Cu1—N1 | 173.25 (9) |
C8—C7—C6 | 119.7 (3) | N2—Cu1—N1 | 82.56 (10) |
C8—C7—H7 | 120.2 | O1—Cu1—Cl1 | 92.28 (6) |
C6—C7—H7 | 120.2 | N2—Cu1—Cl1 | 161.09 (9) |
C7—C8—C9 | 119.9 (3) | N1—Cu1—Cl1 | 94.27 (7) |
C7—C8—N2 | 126.4 (3) | O1—Cu1—Cl1ii | 95.81 (7) |
C9—C8—N2 | 113.8 (3) | N2—Cu1—Cl1ii | 101.29 (8) |
N1—C9—C8 | 117.1 (3) | N1—Cu1—Cl1ii | 85.00 (8) |
N1—C9—C4 | 122.6 (3) | Cl1—Cu1—Cl1ii | 96.97 (3) |
C8—C9—C4 | 120.3 (3) | C1—N1—C9 | 118.0 (3) |
N3—C10—C15 | 113.6 (3) | C1—N1—Cu1 | 129.8 (2) |
N3—C10—C11 | 127.0 (3) | C9—N1—Cu1 | 112.1 (2) |
C15—C10—C11 | 119.4 (3) | N3—N2—C8 | 114.6 (2) |
O1—C11—C12 | 118.9 (3) | N3—N2—Cu1 | 131.0 (2) |
O1—C11—C10 | 122.9 (3) | C8—N2—Cu1 | 114.40 (19) |
C12—C11—C10 | 118.2 (3) | N2—N3—C10 | 120.5 (3) |
C13—C12—C11 | 119.1 (3) | C11—O1—Cu1 | 127.15 (19) |
C13—C12—C16 | 121.0 (3) | C13—O2—H2A | 107 (3) |
C11—C12—C16 | 119.8 (3) | H3W—O3—H4W | 114 (5) |
Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C14—H14···O3 | 0.95 | 2.65 | 3.318 (4) | 128 |
O2—H2A···O3 | 0.82 (4) | 1.87 (4) | 2.686 (4) | 172 (4) |
O3—H3W···Cl1iii | 0.70 (4) | 2.45 (4) | 3.104 (3) | 157 (5) |
O3—H4W···O1iv | 0.89 (6) | 2.20 (6) | 2.911 (4) | 136 (4) |
Symmetry codes: (iii) x+1/2, −y+3/2, z−1/2; (iv) x−1/2, −y+3/2, z−1/2. |
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